1. Technical Field
This invention relates generally to boat hulls, and more particularly to a powered watercraft having a boat hull that is similar in some respects to the M-shaped boat hull designed for the suppression of bow waves described in U.S. Pat. Nos. 6,314,903 and 6,250,245.
2. Description of Related Art
The grandparent and great-grandparent applications of this continuation in part application (Ser. Nos. 09/750,368 and 09/399,468 that issued as U.S. Pat. Nos. 6,314,903 and 6,250,245) describe an M-shaped boat hull designed to overcome certain bow wave concerns. In sea trials of a boat embodying such a hull, the act of increasing power to test the advantages of the air planing cushion at higher boat speeds led to the discovery of two new phenomena. First, the horsepower-to-speed ratio increased in an almost linear form indicating that increased air intake with increasing boat speed enhanced the air cushion planing efficiency so as to offset the exponential increase in wave-making drag with increasing boat speed. Second, the boat operated downwind more efficiently at lower boat speeds, but upwind into a 10-knot breeze the boat was propelled at almost 25% greater speed than when operating downwind. Such unexpected characteristics of an M-shaped boat hull promise significant benefits, and so a need exists for ways to develop and exploit those characteristics.
This invention addresses the need outlined above by providing a watercraft in the form of a boat embodying an M-shaped boat hull design (as we have already patented in U.S. Pat. Nos. 6,250,245 and 6,314,903) that is configured to maximize the volume of air naturally entering the wing channels and to include an air system adapted to inject additional air. So doing, substantially enhances high speed operation and propulsion efficiency and enables a dramatic gain in maximum boat speed.
To paraphrase some of the more precise language appearing in the claims, a watercraft constructed according to the invention includes at least one hull constructed according to the invention as described in our U.S. Pat. Nos. 6,250,245 and 6,314,903. The hull has a fore end, an aft end, a longitudinal axis extending between the fore end and the aft end, and the hull includes a displacement body portion that extends between the fore end and the aft end.
A first channel-defining structure portion of the hull is located on the port side of the displacement body. It includes a first wing structure extending laterally from the port side of the displacement body above the static waterline and a first outer skirt structure that extends downwardly from the first wing structure to below the static waterline in spaced apart relationship to the displacement body. The first outer skirt structure has an outer surface that is substantially perpendicular with respect to the static waterline and the first channel-defining structure defines a first channel with a cross-sectional surface that is generally arcuate.
Similarly, a second channel-defining structure portion of the hull is located on the starboard side of the displacement body. It includes a second wing structure extending laterally from the starboard side of the displacement body above the static waterline and a second outer skirt structure extending perpendicularly downwardly from the second wing structure to below the static waterline in spaced apart relationship to the displacement body. The second outer skirt structure has an outer surface that is substantially perpendicular with respect to the static waterline and the second channel-defining structure defines a second channel with a cross-sectional surface that is generally arcuate.
The first and second channels extend from the fore end to the aft end. The first and second channels are adapted to capture a bow wave and to cause air and water to mix and spiral toward the aft end of the hull as compressed aerated water, thereby reducing friction drag, increasing lateral stability, and dampening transmission of bow wave energy at the aft end of the hull. Those aspects of the watercraft are described and claimed in our U.S. Pat. Nos. 6,314,903 and 6,250,245.
According to a major aspect of the instant invention, the hull has a bow that extends to a vertical knife edge, and the first and second wing channel entrances are arranged to form a near horizontal knife edge at the deck level. That arrangement achieves maximum air flow into the first and wing channels when the watercraft is moving forwardly in order to enhance high speed operation of the watercraft. It improves aerodynamics of the watercraft in order to reduce air resistance during high speed operation of the watercraft. It improves the hydrodynamics at the bow in order to enhance wave piercing during high speed operation of the watercraft. According to another aspect of the invention, there is provided an onboard air system that is adapted to function as means for injecting air into the first and second channels in order to enhance high speed operation of the watercraft. The air system may be configured in any of various ways, including a blower powered by an on-deck onboard or by an auxiliary power unit, a blower powered by a main drive diesel or gas turbine, diverting excess air from a main drive gas turbine, and diverting exhaust from a jet engine main drive.
Thus, the claims for the instant invention are the combination of claims in our patents already issued and added elements directed to the high speed aspects described herein. The instant invention significantly enhances high speed operation of a watercraft embodying an M-shaped boat hull design as we have already patented in U.S. Pat. Nos. 6,250,245 and 6,314,903 by adding structure to a bow-wave capturing hull (i.e., an xe2x80x9cM-shapedxe2x80x9d hull as that term is used in our already issued patents). The invention improves high speed operation and propulsion efficiencies by (i) increasing the volume of air entering the wing channels, thereby enhancing air cushion pressure for more efficient planing, (ii) increasing the aerodynamics of the bow, thereby reducing air resistance, particularly at high boat speeds (iii) improving the hydrodynamics at the bow to allow wave piercing at high boat speeds, and (iv) providing supplemental compressed air to the air cushion for increased efficiency and to allow higher boat speeds. The following illustrative drawings and detailed description make the foregoing and other objects, features, and advantages of the invention more apparent.